Agate (Quartz: Chalcedony) & Gemstones

Agate, is a distinctly banded variety of Chalcedony, is a variety of Quartz gemstones composed of layers of quartz, sometimes of different colors. When it is concentrically banded (often in rather wild patterns) it is called by the subvaritey name "agate." When it is in flat layers/bands it is called by the subvariety name "onyx." Agate usually occurs as rounded nodules or veins in rock such as volcanic lava. The layers of quartz are often concentric. The composition of agate varies greatly, but silica is always predominant, usually with alumina and oxide of iron. Agate comes in most colors. There are several types of agate. Common ones are: blue lace agate, moss agate, tree agate and petrified wood. More on...

The cryptocrystalline varieties of quartz may be separated into two types; fibrous and microgranular. Chalcedony is the general term applied to the fibrous cryptocrystalline varieties. Agate is an example of a fibrous cryptocystalline banded chalcedony variety of quartz. Carnelian, Chrysoprase and bloodstone are other chalcedony varieties.

Chert is the general term applied to the granular cryptocrystalline varieties of quartz, of which flint and Jasper are examples.

It is a mineral generally of secondary origin, forming in cavities and veins by deposition from meteoric groundwater containing gelatinous silica from the weathering of silicate minerals. It can also form by deposition from late hydrothermal solutions at or near the earth's surface under conditions of low temperature and low pressure. Agate is commonly associated with siliceous volcanics, occurring as vein or vesicle filling. It occurs as a petrifying agent in fossil wood and bone. Agate is frequently found lining or filling rock cavities and fissures, sometimes forming geodes.

Colors: Clear, Purple, Rose, Black, Yellow, Brown, Green, Orange, etc.

Lustre: Vitreous

System: Trigonal

Arizona Symbol - Mineral Unofficial

The fire agates from Arizona come from the famous mines, such as Deer Creek, Slaughter Mountain, and others. These agates form in basalt and other volcanics, from a unique process wherein agate is layered in vugs from a hydrothermal solution, one micro-thin layer at a time. Some of these layers diffract light back in a rainbow pattern, creating brilliant bubbles and sheets of red, green, yellow, and the elusive blue.

Kentucky Symbol - Rock adopted in 2000

Fortification Agate with red, black and yellow banding is the US State Rock of Kentucky.

Louisiana Symbol - Gemstone adopted in 1976

Agate is the US State Gemstone of Louisiana.

Minnesota Symbol - Gemstone adopted in 1969

These unusually beautiful quartz stones are banded with rich red and orange colors derived from iron ore in the soil. Found in northeastern and north central Minnesota, they are often polished to make jewelry.

Mississippio Symbol - Stone adopted in 1976

In 1966 the Mississippi Petrified Forest was declared a Registered National Natural Landmark by the National Park Service, Department of the Interior as possessing exceptional value in illustrating the natural history of the United States.

Montana Symbol - Gemstone adopted in 1969

Montana sapphires and Montana agates have shared honors as the state's gemstones since 1969.

Nebraska Symbol - Gemstone adopted in 1967

Commonly called the blue agate, was named Nebraska's state gemstone by legislative action in 1967. A pale stone, blue chalcedony sometimes has a dark internal form with bands of blue and white and often has a colorless streak. Blue agates often are used to make jewelry. The blue agate can be found in northwestern Nebraska.

Nebraska Symbol - Rock adopted in 1967

The prairie agate was declared the Nebraska state rock by legislative action in 1967. Agate is a semiprecious stone, and Nebraska has an abundance of it, especially in the Oglala National Grassland. Agate is a variegated quartz noted for its layered varieties. In most specimens, the bands are very coarse and differ in color and translucency, as well as in compactness and porosity. The prairie agate, distinguished from most other agates because it seldom has these bands, is still colorful, has a rounded irregular shape and is popular for jewelry.

South Dakota Symbol - Gemstone adopted in 1966

The state gemstone is the Fairburn agate, a semiprecious stone first discovered near Fairburn, S.D. The stone is found primarily in an area extending from Orella, Neb., to Farmingdale, S.D. It is used in jewelry and is a favorite of rock collectors.

Tennessee Symbol - Stone adopted in 1969

Agate is the US State Stone of Tennessee.

Washington Symbol - Gemstone adopted in 1975

Petrified Wood is the US State Gemstone of Washington. The geological history of our state has encompassed many great changes, one of them being the many lava flows from volcanic fissures. Centuries ago, the interior of Washington was swampy and mild with many trees such as cypress, oak, elm and gingko growing in wet areas. Layers of logs were preserved with each new lava flow, and as the layers grew deeper, many of the logs became waterlogged and lay protected in deep water. Over time, water continued to seep through the lava and permeate the wood with silica. Eventually, the wood fiber was completely replaced by silica thus petrifying many logs. The petrified wood is perfect in form and detail to the original wood.

Care and Treatment

Since agate is porous, it is often dyed to enhance its natural color. Often treated agate is sold as Black Onyx.

Petrified wood is fossilized wood that has had its organic matter replaced by agate.

Hardness

Agate will chip and crack rather easily though it has a hardness rating of 7.

Hardness (Mohs'): 7
Hardness Data: Measured
Fracture: Conchoidal
Density (measured): 2.65 - 2.66 g/cm3
Density (calculated): 2.66 g/cm3
 

Healing

General: Good for transmutation; helps with the emotion of acceptance; gives a mellow, blended aspect; beneficial in stomach area.
Botswana Agate: Use with high-pressure oxygen therapy; smoke inhalation.
Fire Agate: Master healer with color therapy; enhances all essences; grounds and balances; sexual & heart chakra binder; burns energy.
Moss Agate: Emotional priorities; mental priorities; colon, circulatory, pancreas & pulses; blood sugar balance; agriculture.

Birthstone Months

May: Jupiter/Sagittarius; Ayurvedic Birthstone; 

September: Mercury/Virgo; Mystical Birthstone

Star Stone Months

• Capricorn (Dec 22 - Jan 19): Birthstone
• Aquarius (Jan 20 - Feb 18): Birthstone [Moss Agate]
• Gemini (May 21 - Jun 20): Birthstone, Lucky Charm
• Cancer (Jun 21 - Jul 22): Lucky Charm

Anniversary Gemstone

Agate is the anniversary gemstone for the 12th year of marriage. Moss Agate is the anniversary gemstone for the 14th year of marriage.

 
Mystical Properties

Hindu mystics believe that agate can help children overcome their fears, learn to walk earlier and maintain their balance. Moss Agate is said to help one get in touch with nature. Tree Agate is said to help with introspection. It helps one view themselves with more clarity and see the world through a broader viewpoint.

 
Lore

Agate was highly valued as a talisman or amulet in ancient times. It was said to quench thirst and protect from fevers. Persian magicians used agate to divert storms. A famous collection of two to four thousand agate bowls which was accumulated by Mithradates, king of Pontus, shows the enthusiasm with which agate was regarded.

Legend has it that agate guarded the wearer from all dangers and endowed the wearer with a bold heart.

Wearing Agate was believed to cure insomnia and thought to insure pleasant dreams.